Biogenic fused‑prism CuO nanostructures from medicinal plant extracts for visible‑light photocatalysis and antibacterial activity

A green route to architecturally complex CuO photocatalysts is highly attractive for integrated water disinfection and pollutant removal. Here we report a plant-extract-mediated precipitation–calcination strategy in which aqueous leaf extracts of Mitragyna parviflora and Leptadenia reticulata direct CuO growth from granular nanoparticles into distinctive fused-prism nanostructures (CMP, CLR). X-ray diffraction confirms phase-pure monoclinic CuO for all samples, while FESEM/TEM reveal the evolution from irregular aggregates (extract-free CuO) to faceted plates (CMP) and densely interlocked prisms (CLR). Diffuse reflectance spectroscopy shows marked band-gap narrowing from 2.32 eV (CuO) to 1.35–1.36 eV (CMP, CLR), accompanied by pronounced photoluminescence quenching and subtle changes in Cu 2p and O 1s X-ray photoelectron spectra, indicating altered defect structure and surface oxygen speciation. Under natural sunlight, CLR exhibits the highest photocatalytic activity for Rhodamine 6G, methylene blue and safranine, with apparent rate constants up to 9.81 × 10⁻ 3 min⁻ 1 and simultaneously accelerates 4-chlorophenol degradation compared to CMP and extract-free CuO. Agar well diffusion assays against Escherichia coli (EC), Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) reveal significantly enlarged inhibition zones for the plant-derived samples, particularly CLR, evidencing strong antibacterial activity. These results demonstrate that medicinal plant extracts act as multicomponent structure- and defect-directing media for CuO, yielding fused-prism architectures that couple enhanced visible-light photocatalysis with efficient antibacterial performance.